Couple of questions from a newby

[automationsteed]

Hi all, fairly new here and have a few questions. Firstly, I would like to build my own CNC router setup for sign making.

I am an Engineering Technologist working for a Fluid Power company in Edmonton AB Canada. I program PLC's and HMI now so the electronics should be fairly easy for me, I would like to use Mach3 for software, I have access to a manual mill and welder (I can weld and manual machine) and would very much like to make a cnc unit.

My thought is to make a 48" X 36" inch machine out of steel and aluminum. I want this unit to be fairly ridged to be able to etch 1/4 aluminum sheet on occasion as the shop frequently makes panels and uses colored tape to detail the schematic on the panel, which I think is pretty low tech.

I want to have a fairly decent speed out of the unit, so I am leaning towards rack and pinion on the X & Y axis and acme on the Z axis. I will be using linear bearings on solid steel rod material, (3/4"d on X, 1/2" on Y) which should minimize sag.

Any thoughts on the design?


Automation.

[ger21]

1/2" shafts will flex like a wet noodle, and 3/4" @ 48" long won't be a lot better. Fully supported rails are pretty much mandatory, especially for a machine made of steel.

[dertsap]

have you looked at the mechmate ?
MechMate CNC Router - Build your own with our detailed plans

[Woodbutcher-59]

Hi,

I agree with Gerry, the unsupported rails are not good. My first router is a 24"x 36" with 3/4" pipe for the Y axis and 1" for the X axis....it is okay for alot of stuff but flex is its weakest point. If you can build it with fully supported rails of some sort you will not be sorry.

I consider my first machine an education, and am now building a new one to eliminate the shortcomings of this one. See here in progress...

http://www.cnczone.com/forums/cnc_wo...el_al_3x5.html

Good luck with your project !!!

Jeff

[ahren]

I might humbly suggest our linear motion system which runs on cold rolled steel, and integrates seemlessly with our rack and pinion drive system, which lots of folks here on cnczone have used. It's a lot stiffer than unsupported rails, and less expensive to boot.

CNCRouterParts

Good luck!

Ahren
CNCRouterParts

[automationsteed]

Thanks Ahren, I started looking at your parts yesterday and decided on using your bearing slides. I am going to rethink the design a bit here based on everyones comments.

Thanks for the help folks.

Automation

[automationsteed]

Okay guys, I have put some more thought into the machine design. I am still going with steel for most, some aluminum but here goes.

The attached file is a quick block diagram of what the general layout will look like.

I would like to use 2" steel square tubing for the x-rail - y-rail beds and CNCrouterparts bearing slides to run on 1/4 Flat bar. R&P on both of those. Z axis will be acme rod.

Vertical gantry plates will be Aluminum. Z axis components Alum as well.

X axis travel will be 48", Y axis will be 30" and Z will be 6".

My question is, will I need 2 motors for the X axis or will one do it without binding. I will be using CNCrouterparts Gecko 540 with nema 23 380oz motors.

What do you think.

Auto

[DIYaholic]

automationsteed,

I think you'll need some cross braces for the base in order to support the cutting table. This of course depends upon the material used for the cutting table but most materials will require the additional support.

Good luck designing.

Randy,

[automationsteed]

Thanks DIY, I know that, haven't put it in for simplicity on the drawing. Anyone have any comments on flex of the 2" square tube steel. This unit will be sitting on a steel table when used.

Auto

[CarveOne]

Originally Posted by automationsteed Thanks DIY, I know that, haven't put it in for simplicity on the drawing. Anyone have any comments on flex of the 2" square tube steel. This unit will be sitting on a steel table when used. Auto

I would recommend using the 3/16" (0.180") box tubing instead of 1/8" wall thickness. I'm still amazed at how much flex and twist there is in 1/8" wall steel tubing even in fairly short lengths. If you have a long reach Z axis the 1/8" wall will definitely not be stiff enough at mid span of the gantry. Not so much from sag as from twist from cutting loads.

You will need two carriages on the lower gantry rail. Your drawing seems to show just one.

CarveOne

[jsheerin]

Box in your gantry - don't use two separate beams. It will be way stiffer than how you have it drawn now.

[automationsteed]

Excellent suggestions, I will certainly use them. I have a bunch of 2" X 1/4 wall square tube that will work well for the frame and table bracing. I will use 3/16" on the Y axis rails.

How about one motor or two required to move the gantry on the X-axis?

Auto